來自弗吉尼亞州的愛麗絲-德-斯特勒說，她現在想讓這張署名為 "致媽媽，愛你的柯特 "的卡片與它的主人重聚。
An Agatha Christie novel has yielded its own mystery with the discovery of a hand-drawn Mother's Day card inside - 4,000 miles away.
Alice de Sturler, from Virginia, said she now wants to reunite the card - signed "To mum, love from Kit" - with its owner.
"It's lovely - it was probably used as a bookmark and by accident it was stuck in the book," she added.
"I buy a lot of books online and former library books and when I opened this one, I saw it was from Norfolk."
Ms de Sturler said she thought the paperback had once belonged to the Norfolk Library Service before it was taken off the shelves and sold on.
The card, made from two notepad pages, says "Happy Mother's Day" on the front and features a hand-drawn picture of a red well surrounded by five red flowers.
Ms de Sturler said she decided to contact the BBC on the advice of a UK friend after a social media appeal failed to produce any leads.
A spokesman for Norfolk County Council, which runs the library service, said: "We sell books that are no longer required and in this instance it has provided an extra layer of mystery.
"We would encourage people to ensure no personal items are left in books returned to a library, but we hope that the owner of the card is found."